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NEW QUESTION # 21
Which two statements are true about cursor sharing?

A. Setting Cursor_sharing to FORCE can result in a plan that is suboptimal for the majority of values bound to a bind variable when executing a cursor with one or more bind variables.
B. Setting cursor_sharing to EXACT prevents Adaptive Cursor Sharing from being used.
C. Setting optimizer_capture_sql_plan_baselines to TRUE loads all adaptive plans for the same statement into the cursor cache.
D. Adaptive Cursor Sharing guarantees that a suboptimal plan will never be used on any execution of a SQL statement.
E. Adaptive Cursor Sharing requires histograms on filtered columns, used in equality predicates, to allow different execution plans to be generated for statements whose bound values would normally generate different plans at hard parse time.

Answer: A,B

Explanation:
A: WhenCursor_sharingis set toFORCE, Oracle tries to avoid hard parses by replacing literals in SQL statements with bind variables, even if the original statement didn't include bind variables. This can lead to the use of a single execution plan for multiple executions of a statement with different literal values, which might not be optimal for all executions.
D: Settingcursor_sharingtoEXACTensures that SQL statements must match exactly for them to share a cursor. This setting prevents the use of Adaptive Cursor Sharing (ACS) since ACS relies on the ability to share cursors among similar statements that differ only in their literal values. WithEXACT, there's no cursor sharing for statements with different literals, hence no opportunity for ACS to operate.
References:
* Oracle Database SQL Tuning Guide, 19c
* Oracle Database Reference, 19c

NEW QUESTION # 22
Buffer cache access is too frequent when querying the SALES table. Examine this command which executes successfully:
ALTER TABLE SALES SHRINK SPACE;
For which access method does query performance on sales improve?

A. index full scan
B. db file scattered read
C. index range scan
D. db file sequential read

Answer: D

Explanation:
The SHRINK SPACE operation compacts the table, which can reduce fragmentation and thus improve performance for sequential reads of the table. This operation could improve full table scans, which are typically associated with db file sequential read wait events.
References:
* Oracle Database Administrator's Guide, 19c

NEW QUESTION # 23
A database instance is suffering poor I/O performance on two frequently accessed large tables.
No Big Table caching occurs in the database.
Examine these parameter settings:

Which are two actions either one of which will allow Big Table caching to occur?

A. Increasing DB_BIG_TABLE_CACHE_PERCENT_TARGET to at least 50
B. Increasing DB_CACHESIZE to 1 G
C. Setting DB_KEEP_CACHE_SIZE to at least 50M
D. Setting PARALLEL_DEGREE_POLICYADAPTIVE
E. Setting PARALLEL_DEGREE_POLICYAUTO
F. Increasing DB_BIG_TABLE_CACHE_PERCENT_TARGET to at least 25

Answer: B,F

Explanation:
Big Table caching is a feature that allows frequently accessed large tables to be cached in memory to improve I/O performance. From the parameter settings provided, Big Table caching is not occurring because DB_BIG_TABLE_CACHE_PERCENT_TARGET is set to 10, which is the minimum threshold for enabling the feature, but the size of the cache is too small for the big tables to be effectively cached.
To enable Big Table caching, one of the following actions could be taken:
* C (Correct): Increasing DB_BIG_TABLE_CACHE_PERCENT_TARGET to at least 25. This action would allocate a larger percentage of the buffer cache for storing big tables, which could allow for caching large tables and thus improve I/O performance.
* D (Correct): Increasing DB_CACHE_SIZE to 1G. Since the size of the buffer cache is a determining factor for how much data can be cached, increasing this parameter would provide more memory space for big tables to be cached.
Options A, B, E, and F will not enable Big Table caching because:
* A: Increasing DB_BIG_TABLE_CACHE_PERCENT_TARGET to 50 without adjusting the overall size of the cache might still not be sufficient if the DB_CACHE_SIZE is not large enough to hold the big tables.
* B: Setting DB_KEEP_CACHE_SIZE to at least 50M only specifies a separate buffer pool for objects with the KEEP cache attribute and does not affect Big Table caching.
* E: and F: Changing the PARALLEL_DEGREE_POLICY to ADAPTIVE or AUTO influences the behavior of parallel execution but does not directly enable or influence Big Table caching.
References:
* Oracle Database Performance Tuning Guide: Big Table Caching
* Oracle Database Reference: DB_BIG_TABLE_CACHE_PERCENT_TARGET
* Oracle Database Reference: DB_CACHE_SIZE

NEW QUESTION # 24
The CURS0R_SHARING and OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES parameters are set to default. The top five wait events in an awr report are due to a large number of hard parses because of several almost identical SQL statements.
Which two actions could reduce the number of hard parses?

A. Increase the size of the library cache.
B. Create the KEEP cache and cache tables accessed by the SQL statements.
C. Create the RECYCLE cache and cache tables accessed by the SQL statements.
D. Set OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES to TRUE.
E. Set the CURSOR_SHARING parameter to FORCE.

Answer: A,E

Explanation:
To reduce the number of hard parses due to several almost identical SQL statements, you can take the following actions:
* C (Correct): Increasing the size of the library cache can help reduce hard parses by providing more memory to store more execution plans. This allows SQL statements to be shared more effectively.
* E (Correct): Setting the CURSOR_SHARING parameter to FORCE will cause Oracle to replace literals in SQL statements with bind variables, which can significantly reduce the number of hard parses by making it more likely that similar SQL statements will share the same execution plan.
The other options do not directly impact the number of hard parses:
* A (Incorrect): Creating the KEEP cache and caching tables accessed by the SQL statements can improve performance for those tables, but it does not directly reduce the number of hard parses.
* B (Incorrect): Creating the RECYCLE cache and caching tables accessed by the SQL statements can make it more likely that objects will be removed from the cache quickly, which does not help with hard parse issues.
* D (Incorrect): Setting OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES to TRUE can help stabilize SQL execution plans but will not reduce the number of hard parses. This parameter is used to automatically capture SQL plan baselines for repeatable SQL statements, which can prevent performance regressions due to plan changes.
References:
* Oracle Database Performance Tuning Guide: Minimizing Hard Parses
* Oracle Database SQL Tuning Guide: CURSOR_SHARING

NEW QUESTION # 25
Examine this output of a query of VSPGA_TAPGET_ADVICE:

Which statements is true'

A. With a target of 700 MB or more, all multipass executions work areas would be eliminated.
B. With a target of 800 MB or more, all one-pass execution work areas would be eliminated.
C. GGREGATE_TARGET should be set to at least 700 MB.
D. PGAA_AGGREGATE should be set to at least 800 MB.

Answer: A

Explanation:
The V$PGA_TARGET_ADVICE view provides advice on potential performance improvements by adjusting the PGA_AGGREGATE_TARGET parameter. The column ESTD_OVERALLOC_COUNT indicates the estimated number of work areas that would perform multiple passes if the PGA_AGGREGATE_TARGET were set to the size in the TARGET_MB column.
A: According to the output, at the target of 700 MB, the ESTD_OVERALLOC_COUNT is 30. This suggests that if PGA_AGGREGATE_TARGET is set to 700 MB, 30 multipass execution work areas would be required. If we look further down, at the target of 800 MB, the ESTD_OVERALLOC_COUNT is 0, indicating that increasing PGA_AGGREGATE_TARGET to 800 MB or more would eliminate the need for multipass executions, not at 700 MB as initially suggested by the option. Hence, the verified answer derived from the data is slightly nuanced; it should be 800 MB to eliminate all multipass executions.
References:
* Oracle Database Performance Tuning Guide, 19c
* Oracle Database Reference, 19c

NEW QUESTION # 26
You use SQL Tuning Advisor to tune a given SQL statement.
The analysis eventually results in the implementation of a SQL Profile.
You then generate the new SQL Profile plan and enforce it using a SQL PlanBaselinebut forget to disable the SQLProfile and a few days later you find out that the SQL Profile is generating a new execution plan.
Which two statements are true?

A. The execution plan is the one enforced by the SQL Plan Baseline.
B. The execution plan is the one enforced by the SQL Profile.
C. The conflict between the two plan stability methods results in an error.
D. The SQL Profiles as well as SQL Plan Baseline are implemented using hints, so they both generate the same plan.
E. The SQL Plan Baseline must be accepted in order to be used for the execution plan.
F. The existence of two concurrent plan stability methods generates a child cursor for every execution.

Answer: B,E

Explanation:
When both a SQL Profile and a SQL Plan Baseline are in place, the SQL Profile has a stronger preference and the optimizer is more likely to choose the execution plan from the SQL Profile.
C: A SQL Profile is generally more influential than a SQL Plan Baseline because it contains additional statistics and directives that help the optimizer to generate a more efficient execution plan. If both exist, the optimizer will use the profile's plan unless the baseline's plan is proven to be better through the SQL performance monitoring process.
E: SQL Plan Baselines must be accepted before they can be used by the optimizer. If a SQL Plan Baseline is not accepted, it will not be considered for generating the execution plan. Therefore, the presence of an unaccepted SQL Plan Baseline will not automatically force the optimizer to use its plan.
References:
* Oracle Database SQL Tuning Guide, 19c
* Oracle Database Administrator's Guide, 19c

NEW QUESTION # 27
You need to transport performance data from a Standard Edition to an Enterprise Edition database. What is the recommended method to do this?

A. Export the data by using expdp from the ftatspack repository and import it by using impdp into the AWR repository.
B. Export the data by using expdp from Statspack and import it by using $ORACLE_HOME/rdbms/admin
/awrload into the AWR repository.
C. Export the data by using the exp utility and parameter file spuexp.par from the Statspack repository and import it by using imp into a dedicated Statspack schema on the destination.
D. Export the data by using the expdp utility and parameter file spuexp.par from the Statspack repository and import it by using impdp into Export the data by using expdp from the Statspack repository and import it by using impdp into the AWR repository.

Answer: C

Explanation:
To transport performance data from an Oracle Database Standard Edition, which uses Statspack, to an Enterprise Edition database, which uses AWR, you must consider the compatibility of data structures and repository schemas between these tools. The recommended method is:
* D (Correct): Export the data using the exp utility with a parameter file appropriate for Statspack (like spuexp.par) from the Statspack repository and import it into a dedicated Statspack schema on the destination. Since Statspack and AWR use different schemas, it's not recommended to import Statspack data directly into the AWR repository.
The other options are incorrect because:
* A (Incorrect): expdp is not designed to export from Statspack, and awrload is intended for loading from an AWR export file, not a Statspack export.
* B (Incorrect): Although expdp and impdp are used for exporting and importing data, the AWR repository schema is different from the Statspack schema, so importing Statspack data directly into the AWR repository is not recommended.
* C (Incorrect): Using expdp to export from Statspack and then importing directly into the AWR repository is not the correct approach due to the schema differences between Statspack and AWR.
References:
* Oracle Database Performance Tuning Guide: Migrating from Statspack to AWR

NEW QUESTION # 28
Which two statements are true about space usage in temporary tablespaces?

A. When a global temporary table instantiation is too large to fit in memory, space is allocated in a temporary tablespace.
B. Temporary tablespaces setting Includes quotas to limit temporary space used by a session for that Temporary tablespace.
C. A sort will fail if a sort to disk requires more disk space and no additional extent can be found/allocated in/for the sort segment.
D. Lack of temporary tablespace space for sort operations can be prevented by using temporary tablespace groups.
E. When a session consumes all temporary tablespace storage, then the session would hang until the temporary space used by that session is cleared.

Answer: A,D

Explanation:
Regarding space usage in temporary tablespaces, the following statements are true:
* A (Correct):When a global temporary table or a sort operation exceeds the available memory, Oracle Database allocates space in a temporary tablespace to store the temporary data or intermediate results.
* E (Correct):Using temporary tablespace groups can prevent insufficient temporary tablespace for sort operations by providing a collective pool of space from multiple temporary tablespaces, which can be used for user sorting operations.
The other options provided have inaccuracies:
* B (Incorrect):Oracle does not provide a mechanism for setting quotas on temporary tablespaces. Quotas can be set for permanent tablespaces but not for temporary ones.
* C (Incorrect):A sort operation may fail due to insufficient space, but Oracle will attempt to allocate space in the temporary tablespace dynamically. If no space can be allocated, an error is returned rather than a sort failure.
* D (Incorrect):If a session consumes all available temporary tablespace storage, Oracle will not hang the session; it will return an error to the session indicating that it has run out of temporary space.
References:
* Oracle Database Administrator's Guide:Managing Space for Schema Objects
* Oracle Database Concepts:Temporary Tablespaces

NEW QUESTION # 29
Which three statements are true about server-generated alerts?

A. They provide notifications but never any suggestions for correcting the identified problems.
B. They are logged in the alert log.
C. They may contain suggestions for correcting the identified problems.
D. They are notifications from the Oracle Database Server of an existing or impending problem.
E. Their threshold settings can be modified by using DBMS_SERVER_ALERT.
F. They can be viewed only from the Cloud Control Database home page.

Answer: B,C,D

Explanation:
Server-generated alerts in Oracle Database are designed to notify DBAs and other administrators about issues within the database environment. These alerts can be triggered by a variety of conditions, including threshold-based metrics and specific events such as ORA- error messages. Here's how these options align with the statements provided:
* A (True):Server-generated alerts are indeed notifications from the Oracle Database Server that highlight existing or impending issues. These alerts are part of Oracle's proactive management capabilities, designed to inform administrators about potential problems before they escalate.
* C (True):These alerts are logged in the alert log of the Oracle Database. The alert log is a crucial diagnostic tool that records major events and changes in the database, including server-generated alerts.
This log is often the first place DBAs look when troubleshooting database issues.
* F (True):Server-generated alerts may include suggestions for correcting identified problems. Oracle Database often provides actionable advice within these alerts to assist in resolving issues more efficiently. These suggestions can range from adjusting configuration parameters to performing specific maintenance tasks.
Options B, D, and E do not accurately describe server-generated alerts:
* B (False):While the statement might have been true in some contexts, Oracle's server-generated alerts often include corrective suggestions, making this statement incorrect.
* D (False):Server-generated alerts can be viewed from various interfaces, not just the Cloud Control Database home page. They are accessible through Enterprise Manager, SQL Developer, and directly within the database alert log, among other tools.
* E (False):While it's true that threshold settings for some alerts can be modified, the method specified, usingDBMS_SERVER_ALERT, is not correct. Threshold settings are typically adjusted through Enterprise Manager or by modifying specific initialization parameters directly.
References:
* Oracle Database Documentation:Oracle Database 19c: Performance Management and Tuning
* Oracle Base: Alert Log and Trace Files
* Oracle Support:Understanding and Managing Server-Generated Alerts

NEW QUESTION # 30
Examine this statement and its corresponding execution plan:

Which phase introduces the CONCATENATION step?

A. SQL Semantic Check
B. SQL Row Source Generation
C. SQL Transformation
D. SQL Execution
E. SQL Adaptive Execution

Answer: C

Explanation:
The CONCATENATION step in an execution plan is introduced during the SQL Transformation phase. This phase is part of the optimizer's query transformations which can include various techniques to rewrite the query for more efficient execution. The CONCATENATION operation is used to combine the results of two separate SQL operations, typically when there is an OR condition in the WHERE clause, as seen in the provided query.
References:
* Oracle Database SQL Tuning Guide, 19c
* Oracle Database Concepts, 19c

NEW QUESTION # 31
You want to reduce the amount of db file scattered read that is generated in the database. You execute the SQL Tuning Advisor against the relevant workload. Which two can be part of the expected result?

A. recommendations regarding the creation of materialized views
B. recommendations regarding the creation of SQL Patches
C. recommendations regarding rewriting the SQL statements
D. recommendations regarding the creation of additional indexes
E. recommendations regarding partitioning the tables

Answer: C,D

Explanation:
https://docs.oracle.com/en/database/oracle/oracle-database/21/tgsql/sql-tuning-advisor.html#GUID-
8E1A39CB-A491-4254-8B31-9B1DF7B52AA1
The goal is to reduce the db file scattered read waits, which are associated with full table scans. These are I
/O operations where Oracle retrieves data blocks scattered across the disk, typically when large amounts of data are read inefficiently. Running the SQL Tuning Advisor analyzes the workload and provides tuning recommendations. Let's evaluate the options.
Why A. Recommendations regarding the creation of additional indexes is correct:
* Full table scans (which cause db file scattered read) often occur because suitable indexes are missing.
* The SQL Tuning Advisor can identify queries that would benefit from indexes and recommend creating them. Indexes allow the database to access data more efficiently using row lookups, reducing the need for full table scans.
Why B. Recommendations regarding rewriting the SQL statements is correct:
* Sometimes, poorly written SQL statements cause inefficient execution plans that lead to db file scattered read.
* SQL Tuning Advisor can recommend SQL rewrites to make better use of indexes, avoid full table scans, or optimize joins. For example:
* Rewriting predicates to use indexed columns.
* Using hints to guide the optimizer.
Why Other Options Are Incorrect:
* C. Recommendations regarding the creation of materialized views:
* Materialized views are typically recommended to optimize complex queries involving aggregations or joins, not to address db file scattered read directly. They are less relevant for solving I/O issues caused by full table scans in this context.
* D. Recommendations regarding the creation of SQL Patches:
* SQL Patches are used to influence the execution plan for specific SQL statements. While SQL Patches can potentially fix performance issues, the SQL Tuning Advisor focuses on improving SQL and database design rather than patching queries.
* E. Recommendations regarding partitioning the tables:
* Partitioning tables can improve query performance, especially for very large datasets. However, this is a database design-level recommendation and is not typically provided by SQL Tuning Advisor. Partitioning would not directly target db file scattered read.
How SQL Tuning Advisor Helps:
The SQL Tuning Advisor provides actionable recommendations, such as:
* Creating indexes to reduce full table scans.
* Rewriting SQL to optimize the execution plan.
* Improving statistics to help the optimizer make better decisions.
References to Oracle Documentation:
* Oracle Database 19c Performance Tuning Guide:
* Section: Using SQL Tuning Advisor to Optimize Workloads.
* Explains recommendations for indexes and SQL rewrites to reduce I/O.
* Understanding Wait Events:
* Details about db file scattered read and how to address it.

NEW QUESTION # 32
An Oracle 19c database uses default values for all optimizer initialization parameters.
After a table undergoes partition maintenance, a large number of wait events occur for:
cursor: pin S wait on X
Which command reduces the number of these wait events?

A. ALTER SYSTEM SET CURSOR_SHARING = FORCE;
B. ALTER SYSTEM SET CURSOR_SPACE_FOR_TIME - TRUE;
C. ALTER SYSTEM SET SESSION CACHED CURSORS = 500;
D. ALTER SYSTEM SET CURSOR_INVALIDATION = DEFERRED;

Answer: D

Explanation:
The cursor: pin S wait on X wait event suggests contention for a cursor pin, which is associated with mutexes (a type of locking mechanism) that protect the library cache to prevent concurrent modifications.
This issue can often be alleviated by deferring the invalidation of cursors until the end of the call to reduce contention. The correct command to use would be:
* C (Correct): ALTER SYSTEM SET CURSOR_INVALIDATION=DEFERRED; This setting defers the invalidation of dependent cursors until the end of the PL/SQL call, which can reduce the cursor: pin S wait on X wait events.
The other options are incorrect in addressing this issue:
* A (Incorrect): Setting CURSOR_SHARING to FORCE makes the optimizer replace literal values with bind variables. It doesn't address the contention for cursor pins directly.
* B (Incorrect): CURSOR_SPACE_FOR_TIME=TRUE aims to reduce the parsing effort by keeping cursors for prepared statements open. It may increase memory usage but does not directly resolve cursor: pin S wait on X waits.
* D (Incorrect): Increasing SESSION_CACHED_CURSORS caches more session cursors but doesn't necessarily prevent the contention indicated by the cursor: pin S wait on X wait events.
References:
* Oracle Database Reference: CURSOR_INVALIDATION
* Oracle Database Performance Tuning Guide: Reducing Cursor Invalidation

NEW QUESTION # 33
You must produce a consolidated formatted trace file by combining all trace files generated by all clients for a single service.
Which combination of utilities does this?

A. TKPROF and Trace Analyzer
B. Trcsess and TKPROF
C. Autotrace and TKPROF
D. Trace Analyzer and Tracsess

Answer: B

Explanation:
To produce a consolidated formatted trace file from multiple trace files generated by all clients for a single service, the combination oftrcsessandTKPROFutilities is used. Thetrcsessutility consolidates trace files based on specified criteria such as session, client identifier, or service name. This results in a single trace file that combines the desired tracing information. Next,TKPROFis used to format the output of the trace file generated bytrcsess, providing a readable summary of the trace, including execution counts, execution times, and SQL statement text along with execution plans.
Steps:
* Usetrcsessto combine trace files:
* Command:trcsess output=consolidated.trc service=your_service_name *.trc
* UseTKPROFto format the consolidated trace file:
* Command:tkprof consolidated.trc output.txt explain=user/password sys=no sort=prsela,fchela References:
* Oracle Database Performance Tuning Guide, 19c
* Oracle Database Utilities, 19c

NEW QUESTION # 34
Which two statements are true about disabling Automatic Shared Memory Management (ASMM)?

A. All SGA components excluding fixed SGA and other internal allocations are readjusted immediately after disabling ASMM.
B. The SGA size remains unaffected after disabling ASMM.
C. All SGA components retain their current sizes at the time of disabling.
D. It requires a database instance restart to take effect.
E. All auto-tuned SGA components are reset to their original user-defined values.
F. Both SGA_TARGET and SGA_MAX_SIZE must be set to zero.

Answer: B,C

Explanation:
When ASMM is disabled, the sizes of the automatically managed SGA components remain at their current values. ASMM is controlled by theSGA_TARGETparameter. IfSGA_TARGETis set to a non-zero value, ASMM is enabled and Oracle will automatically manage the sizes of the various SGA components. When ASMM is disabled, by settingSGA_TARGETto zero, the SGA components that were automatically sized will retain their current sizes rather than being reset to their original user-defined values. The overall size of the SGA remains the same unless manually changed by modifying individual component sizes or SGA_MAX_SIZE.
References:
* Oracle Database Administration Guide, 19c
* Oracle Database Performance Tuning Guide, 19c

NEW QUESTION # 35
Examine this statement and output:

Which three statements are true?

A. Both 9822 and 8779 sessions are waiting for operating system resources.
B. Session 8779 may be waiting due to a network problem.
C. Session 9857 waited 1354 seconds for another process, which was also waiting for a transaction to end.
D. Session 9822 will always stop waiting if the session that owns the TX enqueue issues a COMMIT statement as session 9822 is the first session in the transaction queue.
E. Session 8779 may be waiting for a user or application response.
F. Session 9857 is not waiting.

Answer: B,D,E

Explanation:
For this SQL statement and output, we can analyze the EVENT column to understand the type of wait:
B: The event "SQL*Net message from client" typically indicates that the session is waiting for a response from the client. This can be due to a network issue, user response, or an application processing delay.
E: The event "SQL*Net message from client" also implies that the session is idle waiting for the client (a user or an application) to send a request to the server. This event usually indicates that the session is not actively working but is instead waiting for the next command.
F: The wait event "enq: TX - row lock contention" suggests that session 9822 is waiting for a row-level lock held by another session. If the holding session issues a COMMIT or ROLLBACK, the lock will be released, and session 9822 will stop waiting. Since this session is experiencing row lock contention, it implies it's waiting for a specific transaction to complete.
References:
* Oracle Database Reference, 19c
* Oracle Wait Events Documentation

NEW QUESTION # 36
Examine these commands, which execute successfully:

Which statement is true?

A. AWR- snapshots in all pluggable databases will be purgedautomatically after every 60 mins.
B. AWR snapshots can be purged manually in pluggable databases.
C. ADDM, AWR, and ASH reports can be purged automatically.
D. AD DM is enabled for all pluggable databases.

Answer: B

Explanation:
TheDBMS_WORKLOAD_REPOSITORY.MODIFY_SNAPSHOT_SETTINGSprocedure allows setting attributes related to AWR snapshots. While the interval setting controls the frequency of snapshot generation, purging them is a separate process that can be managed either automatically (with retention settings) or manually.References:
* Oracle Database PL/SQL Packages and Types Reference, 19c
* Oracle Multitenant Administrator's Guide, 19c

NEW QUESTION # 37
Multiple sessions are inserting data concurrently into a table that has an LOB column.
At some point in time, one of the sessions cannot find available space in the LOB segment and needs to allocate a new extent.
Which wait event will be raised in the other sessions that need space in the LOB column?

A. enq: TM - contention
B. enq: TX - allocate ITL entry
C. enq: SQ - contention
D. enq: HW - contention

Answer: D

Explanation:
When sessions concurrently insert data into a table with an LOB column and one session needs to allocate a new extent because it cannot find available space, the wait event associated with this contention is "enq: HW - contention". The HW stands for High Water Mark which is related to space allocation in the database segment. When a session needs to allocate a new extent, it may raise this wait event in other sessions that are also attempting to allocate space in the same LOB segment.
References
* Oracle Database 19c Reference Guide - enq: HW - contention

NEW QUESTION # 38
Examine this statement and output:

Which three statements are true?

A. Both 9822 and 8779 sessions are waiting for operating system resources.
B. Session 8779 may be waiting due to a network problem.
C. Session 9857 waited 1354 seconds for another process, which was also waiting for a transaction to end.
D. Session 9822 will always stop waiting if the session that owns the TX enqueue issues a COMMIT statement as session 9822 is the first session in the transaction queue.
E. Session 8779 may be waiting for a user or application response.
F. Session 9857 is not waiting.

Answer: B,D,E

Explanation:
For this SQL statement and output, we can analyze theEVENTcolumn to understand the type of wait:
B: The event "SQL*Net message from client" typically indicates that the session is waiting for a response from the client. This can be due to a network issue, user response, or an application processing delay.
E: The event "SQL*Net message from client" also implies that the session is idle waiting for the client (a user or an application) to send a request to the server. This event usually indicates that the session is not actively working but is instead waiting for the next command.
F: The wait event "enq: TX - row lock contention" suggests that session 9822 is waiting for a row-level lock held by another session. If the holding session issues a COMMIT or ROLLBACK, the lock will be released, and session 9822 will stop waiting. Since this session is experiencing row lock contention, it implies it's waiting for a specific transaction to complete.
References:
* Oracle Database Reference, 19c
* Oracle Wait Events Documentation

NEW QUESTION # 39
A database supporting a mixed workload is hosted on a server with 64 CPUs.
A large number of free buffer waits and buffer busy waits occur affecting performance.
The buffer cache size was then increased but after a few hours, the same wait events occur more often than before the change.
Examine these parameter settings:

Which two actions can help reduce the number of these waits7

A. setting dbwr_io_slaves to 64
B. increasing the value of DB_FILE_MULTIBLOCK_READ_COUNT to 128
C. increasing the value of DBWRITERPROCESSES to 64,
D. Increasing the size of MEMORYTARGET
E. reducing the values of DB_FILE_MULTILOCK_READ_COUNT to 64

Answer: A,C

Explanation:
Given a server with 64 CPUs, if the buffer cache size increase did not alleviate free buffer waits and buffer busy waits, one can look into optimizing I/O and the efficiency of the DB writer processes.
C: Setting the DBWR_IO_SLAVES parameter to a non-zero value, such as the number of CPUs, would initiate I/O slave processes to assist the DB writer process. This can help reduce I/O contention when writing from the buffer cache to disk, particularly for systems without asynchronous I/O capabilities.
D: Increasing the value of DBWRITERPROCESSES enables multiple DB writer processes to be active simultaneously. In a system with many CPUs, such as 64, increasing this value can improve the write throughput to disk and potentially reduce buffer busy waits.
References:
* Oracle Database Reference, 19c
* Oracle Database Performance Tuning Guide, 19c

NEW QUESTION # 40
Multiple sessions are inserting data concurrently into a table that has an LOB column.
At some point in time, one of the sessions cannot find available space in the LOB segment and needs to allocate a new extent.
Which wait event will be raised in the other sessions that need space in the LOB column?

A. enq: TM - contention
B. enq: TX - allocate ITL entry
C. enq: SQ - contention
D. enq: HW - contention

Answer: D

Explanation:
When sessions concurrently insert data into a table with an LOB column and one session needs to allocate a new extent because it cannot find available space, the wait event associated with this contention is "enq: HW - contention". The HW stands for High Water Mark which is related to space allocation in the database segment.
When asession needs to allocate a new extent, it may raise this wait event in other sessions that are also attempting to allocate space in the same LOB segment.
References
* Oracle Database 19c Reference Guide - enq: HW - contention

NEW QUESTION # 41
What is the right time to stop tuning an Oracle database?

A. When the allocated budget for performance tuning has been exhausted
B. When all the concurrency waits are eliminated from the Top 10
C. When the I/O is less than 10% of the DB time
D. When the buffer cache and library cache hit ratio is above 95%
E. When the tuning goal has been met

Answer: E

Explanation:
The objective of performance tuning in Oracle Database is to meet specific performance goals. These goals may vary based on the requirements of the system and business objectives. Let's evaluate each option in detail to understand why E is correct and others are not.
Option Analysis:
* A. When the allocated budget for performance tuning has been exhausted
* Why it's incorrect:
* Tuning should not stop simply because the budget is exhausted. If performance goals are not met, the database might still experience performance issues, impacting the end-users or business-critical processes. Budget is a constraint, but it shouldn't define when tuning stops.
* B. When all the concurrency waits are eliminated from the Top 10
* Why it's incorrect:
* Concurrency waits (such as locks or latches) are just one aspect of database performance tuning. Eliminating these waits does not necessarily mean the system meets its performance goals. Other factors like query optimization, I/O performance, and CPU usage might still need attention.
* C. When the buffer cache and library cache hit ratio is above 95%
* Why it's incorrect:
* Cache hit ratios are often overemphasized as a performance metric. While a high hit ratio indicates efficient memory usage, it doesn't guarantee optimal performance. A high ratio could still mask inefficient SQL queries, suboptimal execution plans, or other bottlenecks.
* D. When the I/O is less than 10% of the DB time
* Why it's incorrect:
* While reducing I/O is beneficial, it is not always a sufficient indicator that tuning can stop.
Certain workloads may inherently have high or low I/O percentages. The real question is whether the database is meeting its required service levels, not just reducing I/O.
* E. When the tuning goal has been met
* Why it's correct:
* The purpose of performance tuning is to meet the specific performance goals set by the business or the database administrators. Once the database meets these goals (e.g., query response times, throughput requirements, or SLA commitments), tuning can stop. This ensures effort is focused on achieving measurable outcomes, rather than chasing arbitrary metrics.
The Importance of Defining a Tuning Goal
Performance tuning should be driven by clear goals such as:
* Reducing response time for specific critical queries.
* Meeting SLAs for application performance.
* Supporting a target number of concurrent users.
* Reducing resource contention for improved scalability.
Tuning should stop once these goals are achieved because continuous tuning without purpose can lead to unnecessary complexity and resource usage.
Reference to Oracle Documentation:
* Oracle Database 19c Performance Tuning Guide:
* Section: Establishing Performance Goals and Metrics.
* Discussion on focusing tuning efforts on business requirements and goals.
* Oracle Database Concepts Guide:
* Best practices for balancing performance improvements with system complexity.

NEW QUESTION # 42
Examine this statement and its corresponding execution plan:

Which phase introduces the CONCATENATION step?

A. SQL Semantic Check
B. SQL Row Source Generation
C. SQL Transformation
D. SQL Execution
E. SQL Adaptive Execution

Answer: C

NEW QUESTION # 43
What is the right time to stop tuning an Oracle database?

A. When all the concurrency waits are eliminated from the Top 10
B. When the I/O is less than 10% of the DB time
C. When the allocated budget for performance tuning has been exhausted
D. When the buffer cache and library cache hit ratio is above 95%

Answer: C

Explanation:
The right time to stop tuning an Oracle database is often determined by the point of diminishing returns - when the cost of further tuning (in terms of time, resources, or money) exceeds the performance benefits gained.
This is often related to the budget allocated for performance tuning.
* A (Correct):When the allocated budget for performance tuning has been exhausted, it may be time to stop tuning unless the benefits of further tuning justify requesting additional budget.
* B (Incorrect):Eliminating all concurrency waits from the Top 10 is an unrealistic goal since some waits are inevitable and can occur due to application design, which might not be possible to eliminate completely.
* C (Incorrect):The buffer cache and library cache hit ratio being above 95% does not necessarily indicate that the database is fully optimized. Hit ratios are not reliable indicators of database performance and should not be used as sole criteria to end tuning efforts.
* D (Incorrect):Having I/O less than 10% of DB time is not a definitive indicator to stop tuning. It is essential to consider the overall performance goals and whether they have been met rather than focusing solely on I/O metrics.
References:
* Oracle Database Performance Tuning Guide:Introduction to Performance Tuning
* Oracle Database 2 Day + Performance Tuning Guide:Understanding the Tuning Process

NEW QUESTION # 44
Accessing the SALES tables causes excessive db file sequential read wait events.
Examine this AWR except:

Now, examine these attributes displayed by querying dba_tables:

Finally, examine these parameter settings:

Which two must both be used to reduce these excessive waits?

A. Re-create the SALES table.
B. Increase PCTFREE for the SALES table.
C. Compress the SALES table.
D. Partition the SALES table.
E. Coalesce all sales table indexes.

Answer: C,D

Explanation:
The AWR excerpt points to excessive physical reads on the SALES table and index, suggesting the need for optimizing table storage and access.
Partitioning the SALES table (A) can reduce 'db file sequential read' waits by breaking down the large SALES table into smaller, more manageable pieces. This can localize the data and reduce the I/O necessary for query operations.
Compressing the SALES table (D) can also help reduce I/O by minimizing the amount of data that needs to be read from disk. This can also improve cache utilization and reduce the 'db file sequential read' waits.
References:
* Oracle Database VLDB and Partitioning Guide, 19c
* Oracle Database Administrator's Guide, 19c
These changes are recommended based on Oracle's best practices for managing large tables and reducing I/O waits, ensuring better performance and efficiency.

NEW QUESTION # 45
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